Question

I need to write blocks of data (characters) and I don’t care about the sequence of those blocks. I wonder what kind of OutputStream I should use to achieve high performance?

Answer 1

Simply calling a vanilla ZipOutputStream from multiple threads would not work. The ZipOutputStream API has a model where you write entries one at a time as follows:

ZipOutputStream zos = ...

while (...) {
    zos.putNextEntry(...);
    while (...) {
       zos.write(...);
    }
    zos.closeEntry();
}

This model is inherently non-thread-safe.

In order to do this in a thread-safe fashion, you’d need to wrap the ZipOutputStream in a class that does the put/write/close operations in one synchronized method call. And that means that you are essentially doing your Zip output operations serially, which largely defeats your purpose for doing this.